The present invention relates, in general, to test systems and, more particularly, to self test systems for ground fault interrupters.
Ground fault circuit interrupters are included in electrical systems to protect individuals in case a fault occurs. It is desirable to test ground fault circuit interrupters to ensure that they are functioning properly. Methods for testing these circuits have been described in U.S. Pat. No. 8,085,516 titled “Ground Fault Circuit Interrupter with Self Test” issued to Bruce G. Armstrong on Dec. 27, 2011, and U.S. Pat. No. 7,911,746 titled “GFCI with Self-Test and Remote Annunciation Capabilities” issued to Albert Zaretsky et al. on Mar. 22, 2011. Although these approaches provide self test capabilities, they do not address various types of faults that may occur.
Accordingly, it would be advantageous to have a circuit and method for performing self tests in ground fault circuit interrupters. It would be of further advantage for the circuit and method to be cost efficient to implement.
For simplicity and clarity of illustration, elements in the figures are not necessarily to scale, and the same reference characters in different figures denote the same elements. Additionally, descriptions and details of well-known steps and elements are omitted for simplicity of the description. It will be appreciated by those skilled in the art that the words during, while, and when as used herein are not exact terms that mean an action takes place instantly upon an initiating action but that there may be some small but reasonable delay, such as a propagation delay, between the reaction that is initiated by the initial action and the initial action. The use of the words approximately, about, or substantially means that a value of an element has a parameter that is expected to be very close to a stated value or position. However, as is well known in the art there are always minor variances that prevent the values or positions from being exactly as stated.
It should be noted that a logic zero voltage level (VL) is also referred to as a logic low voltage or logic low voltage level and that the voltage level of a logic zero voltage is a function of the power supply voltage and the type of logic family.